1. Field of the Invention
The present invention relates to a thermoplastic packaging comprising at least one inner layer and one outer layer, which is especially suited to contain cosmetic or dermatological compositions and serves to protect the contents from light radiation and from oxidation, while at the same time having a satisfying aesthetic appearance, and a process for the production of the packaging.
2. Discussion of the Background
EP-A-0 204 324 discloses a multilayer pad, the thermoplastic outer layer of which comprises an inorganic filler. However, this filler must have a very small particle size and does not provide a satisfying aesthetic appearance.
FR-A-2 657 048 teaches a process for manufacturing packaging which has a natural-stone external appearance and having a wall which consists of a monolayer thermoplastic matrix which includes at least two fillers of different sizes or particle sizes.
These types of thermoplastic packaging are obtained by means of known shaping processes of the injection-molding type.
Unfortunately, the fillers are not always distributed uniformly in the matrix and are not always present in sufficient quantity to impart a satisfying stone appearance. Indeed, too large a quantity of filler in the material leads to a reduction in the elasticity of the material and can cause the appearance of holes and/or cracks in the wall of the packaging. This leads to increased air permeability of the wall, which can lead to degradation of the contents of the packaging.
Likewise, the presence of particles of large diameter, especially greater than the thickness of the wall, may cause holes and/or cracks. However, to impart a suitable stone appearance, it is necessary to use a large quantity of filler, having a large and varied particle size.
Other techniques for shaping plastics, such as coextrusion or coextrusion/blowing are known for unfilled plastics. These techniques consist in simultaneously extruding several plastics through the same die. They can be used to obtain components whose various materials constituting the inner and outer walls do not mix and remain uniformly distributed. These techniques have the advantage of being able to use two different materials for the inner and outer walls of the packaging.
This technique is especially described in U.S. Pat. No. 4,292,355 for the manufacture of a plastic container, consisting only of a polypropylene layer and a butadiene styrene polymer layer.
Unfortunately, this choice of material does not enable fillers to be added to the materials constituting the outer layer.
Accordingly, one object of the present invention is to provide thermoplastic packaging which is hermetic with respect to air and to its contents, and is capable of providing a stone appearance.
A further object of the present invention is to provide thermoplastic packaging which can be used to contain cosmetic or dermatological compositions.
A further object of the present invention is to provide a thermoplastic multilayer packaging which is free of cracks and includes at least one inner wall and one outer wall, the outer layer of which includes at least one filler.
A further object of the present invention is to provide a process for producing the multi-layer packaging of the present invention.
These and other objects of the present invention have been satisfied by the discovery of a thermoplastic packaging comprising at least one thermoplastic inner layer and one thermoplastic outer layer, wherein the outer layer is crack-free and comprises at least one filler having particles of variable particle size and particle diameters xe2x89xa750 xcexcm, and a process for the production of the thermoplastic packaging by coextrusion/blowing.
The present invention relates to a thermoplastic packaging comprising at least one thermoplastic inner layer and one thermoplastic outer layer, the outer layer being crack-free and comprising at least one filler containing particles of different particle size and of a diameter greater than 50 xcexcm.
The present invention also relates to a process for manufacturing a packaging obtained by coextrusion of at least two layers, which comprises coextruding a thermoplastic inner layer and an outer layer containing particles of variable particle size and of a diameter greater than 50 xcexcm, then blowing the outer layer so that the particles of the filler orient parallel to the inner layer and cause no cracking of the packaging.
This process can indeed be used to obtain crack-free packaging having an outer layer with particles of diameter greater than 50 xcexcm, contrary to the process described in FR-A-2 657 048,
According to the present invention, it is possible to use one or more inner layers associated with one or more outer layers, at least one of which is filled.
Preferably, the particles of the filler have a diameter ranging from 50 xcexcm to 3 mm, more preferably ranging from 80 xcexcm to 1.5 mm, and most preferably from 150 xcexcm to 600 xcexcm.
The packaging according to the present invention may use fillers having lamellar particles without fear of cracks or holes in the wall. The reason for this is that lamellar particles, once in contact with the inner layer, orient parallel to this inner layer along their length during the blowing process.
The coextruded inner layer serves for maintaining the filled material constituting the inner wall during the blowing of this filled material, thus orienting the particles appropriately.
By using the coextrusion/blowing technique, the thickness of the inner layer may represent up to approximately 80% of the total thickness of the packaging, contributing towards obtaining a satisfying stone appearance. The outer layer can have a thickness representing between 20% and 50% of the total thickness of the packaging. In order to obtain a smooth, natural-stone external appearance, the outer layer preferably has a thickness representing between 20% and 30% of the total thickness of the packaging.
In order to obtain a natural-stone external appearance with a rough surface, the outer layer preferably has a thickness representing between 30% and 50% of the total thickness of the packaging. This result may be useful for obtaining packaging with a wall in relief.
In fact, the thicker the outer layer is the more matt its color becomes, and the more rough its surface becomes, with the particles constituting the filler no longer orienting parallel to the inner wall. In such cases, the inner wall no longer plays a significant role for orienting the particles during the blowing of the filled material.
The outer layer preferably has a thickness of 0.1 mm to 0.8 mm, more preferably of 0.2 mm to 0.5 mm. The inner layer preferably has a thickness of 0.5 mm to 1.3 mm, more preferably of 0.6 mm to 1.0 mm.
The materials constituting the layers must fulfill certain criteria. They must especially be mutually compatible and allow incorporation of filler in one of them.
The inner layer is preferably made of a material compatible with the contents, so as to prevent them from degrading, and most preferably should be inert with respect to chemical compositions preferentially used in the cosmetic and dermatological fields. The material used in the inner layer is preferably a thermoplastic elastomer chosen from low-density polyethylenes, high-density polyethylenes and polypropylenes.
The material of the outer layer is preferably a material capable of protecting the contents from light radiation and from oxidation. It is most preferably a blowing-grade thermoplastic chosen from polypropylenes, polyethylenes, polyesters and polypropylene copolymers such as the products marketed under the same HIFAX(trademark) or PROFAX(trademark) by the HIMONT company.
The material constituting the inner layer is preferably tinted and the layer of the material constituting the outer layer is preferably opaque or translucent. When the inner layer is tinted and the outer layer is translucent, a bright vivid color is obtained for the packaging.
The filler or fillers incorporated into the material forming the outer layer are preferably chosen from mineral fillers, vegetable fillers or a mixture thereof.
Among mineral fillers, it is preferred to use calcium carbonate, calcium sulphate, zinc oxide, zinc carbonate, magnesium oxide, magnesium hydroxide, magnesium silicates such as talc, aluminum silicates such as mica, glass microballs or aluminum flakes.
Among vegetable fillers, it is preferred to use natural fibers, such as wood, cellulose or cotton fibers or particles. The particle size or diameter of the fillers preferably ranges from 50 xcexcm to 3 mm and more preferably ranges from 80 xcexcm to 1.5 mm.
The filler or fillers may or may not be colored. The coloring may be obtained by impregnating the particles of the filler with a colorant, such as a liquid or pulverulent colorant. The colorant is chosen so as to withstand the melting temperature of the polymer constituting the outer layer. This colorant may be fixed to the filler and/or coated with a thermosetting resin, such as urea/formaldehyde copolymer, or with a polymer of the acrylic or vinyl type, obtained by in situ polymerization on the filler, or else fixed according to the process described in FR-A-4 651 789.
Introducing a colored filler into a translucent or white material constituting the outer layer does not modify the color of the material. This also applies for a colored material and a colorless filler.
By the appropriate and combined choice on the one hand, of the color, the amount and the particle size of the filler, and on the other hand, of the color of the material forming the outer layer, it is possible to obtain, in a reproducible manner, a uniform distribution of the filler in the material and to give it a natural-stone external appearance.
The outer layer of the packaging according to the invention may be obtained by preparing a mixture of various fillers, just as they are cr in a preblend form, and then by incorporating these fillers into the material forming the outer layer.
The material constituting the inner layer and that of the filled outer layer are coextruded and then blown, the inner layer subsequently pushing the fillers of the outer layer and orienting them parallel to the wall of the packaging.
The packaging of the present invention may be in any desired shape, preferably in the form of a flask, pot or bottle, with a flask having a natural stone appearance being most preferred.
The invention also relates to a process for manufacturing a thermoplastic packaging obtained by coextrusion of at least two layers, comprising coextruding a thermoplastic inner layer and an outer layer containing at least one filler containing particles of variable particle size of a diameter greater than 50 xcexcm, and blowing the two layers so that particles of the filler in the outer layer orient parallel to the inner layer.
Having generally described this invention, a further understanding can be obtained by reference to certain specific examples which are provided herein for purposes of illustration only and are not intended to be limiting unless otherwise specified.